Introduction

This repository contains a Torch implementation for the ResNeXt algorithm for image classification. The code is based on fb.resnet.torch.

ResNeXt is a simple, highly modularized network architecture for image classification. Our network is constructed by repeating a building block that aggregates a set of transformations with the same topology. Our simple design results in a homogeneous, multi-branch architecture that has only a few hyper-parameters to set. This strategy exposes a new dimension, which we call “cardinality” (the size of the set of transformations), as an essential factor in addition to the dimensions of depth and width.

Figure: Training curves on ImageNet-1K. (Left): ResNet/ResNeXt-50 with the same complexity (~4.1 billion FLOPs, ~25 million parameters); (Right): ResNet/ResNeXt-101 with the same complexity (~7.8 billion FLOPs, ~44 million parameters).

Note: CIFAR datasets will be automatically downloaded and processed for the first time. Note that in the arXiv paper CIFAR results are based on pre-activated bottleneck blocks and a batch size of 256. We found that better CIFAR test acurracy can be achieved using original bottleneck blocks and a batch size of 128.